在 DB2 中拆分 VARCHAR 以检索其中的值 [英] Split a VARCHAR in DB2 to retrieve a value inside

问题描述

我有一个 VARCHAR 列，其中包含 5 个信息(2 个 CHAR(3) 和 3 个 TIMESTAMP)，用 '$ 分隔'.

I have a VARCHAR column that contains 5 informations (2 CHAR(3) and 3 TIMESTAMP) separated with '$'.

CREATE TABLE MYTABLE (
  COL VARCHAR(256) NOT NULL
);

INSERT INTO MYTABLE 
VALUES
    ( 'AAA$000$2009-10-10 10:50:00$null$null$null' ),
    ( 'AAB$020$2007-04-10 10:50:00$null$null$null' ),
    ( 'AAC$780$null$2007-04-10 10:50:00$2009-04-10 10:50:00$null' )
;

我想提取第四个字段...

I would like to extract the 4th field ...

'AAA$000$2009-10-10 10:50:00$null$null$null'
                             ^^^^ this field

...拥有类似的东西

SELECT SPLIT(COL, '$', 4) FROM MYTABLE

1
-----
'null'
'null'
'2009-04-10 10:50:00'

我正在按顺序搜索:

1. 一个 DB2 内置字符串函数
2. 可嵌入语句，例如SUBSTR(COL, POSSTR(COL)+1)...
3. 用户定义的函数，其行为类似于 SPLIT

精确度:是的，我确实知道拥有这样的列不是一个好主意...

Precision : Yes, I do know that it's not a good idea to have such columns...

推荐答案

CREATE FUNCTION split(pos INT, delimeter CHAR, string VARCHAR(255))
LANGUAGE SQL
RETURNS VARCHAR(255)
DETERMINISTIC NO EXTERNAL ACTION
BEGIN ATOMIC
    DECLARE x INT;
    DECLARE s INT;
    DECLARE e INT;

    SET x = 0;
    SET s = 0;
    SET e = 0;

    WHILE (x < pos) DO
        SET s = locate(delimeter, string, s + 1);
        IF s = 0 THEN
            RETURN NULL;
        END IF;
        SET x = x + 1;
    END WHILE;

    SET e = locate(delimeter, string, s + 1);
    IF s >= e THEN
        SET e = LENGTH(string) + 1;
    END IF;
    RETURN SUBSTR(string, s + 1, e - s -1);
END!

用法:

SELECT split(3,'$',col) from mytable; -- or
SELECT split(0,'-', 'first-second-third') from sysibm.sysdummy1;
SELECT split(0,'-', 'returns this') from sysibm.sysdummy1;
SELECT split(1,'-', 'returns null') from sysibm.sysdummy1;

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